Sensor to read LED flash on back of a camera

WHall

I recently purchased the Board of Education and am working through the first few lessons in the What's a Microcontroller? book. Ultimately, I'd like to build a mechanism that would take pictures for a high altitude balloon payload I'm working on. I'm using an intervalometer (CHDK) to script the Canon A570 camera to take a series of timed images. I'd also like to use a sensor (taped to the camera) to read the flash of a white LED (on the back of the camera, next to the optical viewfinder) into the Basic Stamp 2, which would pulse, in turn, a servo to reorient the camera. I've searched the forums and the Parallax site, but I'm still confused (sorry!) as to what sensor, if any, might see the flash that would indicate a picture has been snapped. I'm just getting started - a fact that will probably not surprise anyone who's read this post - but any thoughts on what sensor to use would be very much appreciated.

kf4ixm

depending on the brightness of the led, you could use another white led in reverse-bias mode to generate a voltage for the stamp to detect the led you want to monitor.· attach a white led to a volt meter, hold the led to the one on the camera while its on and observe the voltmeter reading to confirm.

WHall

That strikes me a really simple and elegant solution kf4ixm. Thanks! I'll give it a try.

kf4ixm

if you have one, try using a flat-top led, it will focus the avaliable light better to the diode.

WHall

Will definitely keep that in mind, kf4ixm. Thanks so much!

Wildatheart

As I understand it, an intervalometer is a timing mechanism. If that's true, how are you activating the shutter of the A570?

WHall

The intervalometer is a timing script that can be run in conjunction with the CHDK firmware loaded *temporarily* via SD card. When the card is removed, the firmware is removed and the camera reverts to its original firmware state. If you're taking a camera to 100,00 feet, you need it to work unattended. CHDK itself enables extremely fast shutter speeds, motion detection, live histograms, etc., making the camera much more capable. I'm primarily interested in the intervalometer though.

Peter KG6LSE

I don't know If what I did a few months ago could be of any use to you but feel free to hack my code . its for time lap's

http://forums.parallax.com/showthread.php?p=861003

but I second every one else s idea of the LED .
Also a small solar cell could be used too .. the shack has a small one you can cut (break) in to smaller peaces to use as a over-sized photocell.


Peter KG6LSE

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"Carpe Ducktum" "seize the tape!!"
peterthethinker.com/tesla/Venom/Venom.html
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LOL

WHall

Peter, thanks for the pointer! Going to try the LED to send the signal from the back of the camera to the stamp. I'll let everyone know how it goes when I get that far.

jeff2.0

I did a tally light project on some video cameras·this week for my church.

I captured the output of a small existing·LED optically by glueing a photo transistor over it and had it·fire a transistors base·to switch·voltage to·LEDs both in front of the camera and in front of the camera operator (to replace the one I covered up).

It worked great.

I would think that this method could easily trigger a stamp as well.

jeff

WHall

Jeff2.0, thanks for sharing!